Reflective-transmission type thin film transistor liquid crystal display with non-oxidizing metal layer in first pixel electrode

ABSTRACT

The present invention provide a reflective-transmission type TFT LCD wherein each of the reflective pixel electrode and the transmissive pixel electrode is connected directly to a source electrode of a thin film transistor, or the transmissive pixel electrode are concurrently formed with gate electrode and made with double layer of transparent conduction layer and metal layer which can be used as parameter conduction layer between the transparent conduction layer and the reflective pixel electrode. According to one aspect of the present invention, the reflective transmission type thin film transistor liquid crystal display (TFT LCD) comprises a glass substrate, at least one thin film transistor on the substrate for controlling a pixel, passivation layer having at least one contact hole in a source region of the thin film transistor, a transmissive pixel electrode which is formed on the passivation layer and is connected with a source electrode of the source region through a contact hole, a reflective pixel electrode which is formed on the passivation layer and is connected with the source electrode of the source region through a contact hole. And the pixel area is composed of a transparent area in which only the transmissive pixel electrode of whole pixel electrode exist and a reflective area in which the reflective pixel electrode exist.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 09/709,312, filed Nov. 13, 2000, and issued as U.S.Pat. No. 6,683,666, which claims priority from Korean Patent ApplicationNo. 1999-49940 filed Nov. 11, 1999, and Korean Patent Application No.2000-11533 filed Mar. 8, 2000, which are all hereby incorporated byreference for all purposes as if fully set forth herein.

FIELD OF THE INVENTION

The present invention is related to reflective-transmission type thinfilm transistor liquid crystal display and more specifically related toliquid crystal display wherein the reflective pixel electrode andtransmissive pixel electrode composing the whole pixel electrode can bestably connected with the source electrode of thin film transistor whichcontrols a pixel.

BACKGROUND OF THE INVENTION

Liquid crystal displays can be classified to many numerous typesaccording to the methods of manufacturing and the structures. Forexample, top gate type and bottom gate type can be deferentiated. Forthe manufacturing of top gate type LCD, active layer made withsemiconductor material is formed before gate insulating layer and gatepattern are formed. But, in case of bottom gate type LCD, the gatepattern and the gate insulating layer is formed prior to the activelayer.

On the other hand, the classification of reflective type andtransmissive type can be possible. In the transmissive type LCD, thepixel electrode is made with reflective materials like metals whichreflect light from external environment. But, in the reflective typeLCD, the pixel electrode is made with transparent conductive materialscontaining indium metal oxide lineage like ITO (indium tin oxide). Inthe transmissive type LCD, independent light source is placed at thebackside of LCD panel and thus called backlight, and various colorfulimages can be presented by controlling the state of liquid crystal ofnumerous pixels to transmit or to shied the light from the backlight.

Recently, reflective type LCD is considered as an alternative innotebook LCD which need large display size and high quality image. Andreflective-transmission type LCD which has merits of both reflectivetype and transmission type is also presented by SHARP(registered trademark).

In the reflective transmission type LCD of SHARP, transmissive pixelelectrode is formed to be connected to source electrode of thin filmtransistor in the process of making thin film transistor on glasssubstrate. And passivasion layer which has contact hole in the sourceregion of the thin film transistor is formed on the thin filmtransistor. Then, reflective metal layer like aluminum is formed on thepassivation layer and patterned to confine the reflective area and toform a window which reveals some part of transmissive layer. Here, thepatterned reflective metal, the reflective pixel electrode is connectedto the source electrode through the contact hole.

Meanwhile, in the process of fabricating the reflective transmissiontype LCD, some problems can be caused according to the materials adoptedas transmissive pixel electrode and reflective pixel electrode. Forexample, if the reflective pixel electrode made with aluminum, iselectrically connected with the source electrode by the transmissivepixel electrode which covers the source electrode. But, the transmissivepixel electrode is made with ITO (indium tin oxide) generally used astransparent conduction layer, an oxide insulation layer is to be formedbetween the reflective pixel electrode and transmissive pixel electrode.Then, the oxide layer prevents the enhancement of electric field to thereflective pixel electrode.

To avoid the problem, a parameter conduction layer can be used at theinterface of the two problematic electrode materials. Also, the twoproblematic pixel electrode may be connected to the source electrode atdifferent positions to prevent the problem. However, compared with therelatively large pixel electrode area, the region of the sourceelectrode is confined to relatively small area, which makes it difficultto design and to form the transmissive area and the reflective areaproperly and simply.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide areflective transmission type TFT LCD wherein the stable operation ofwhole pixel electrode and safe enhancement of electric potential towhole pixel electrode can be confirmed.

It is another object of the present invention to provide a reflectivetransmission type TFT LCD wherein the easiness and simplicity can besustained in the process of forming the whole pixel electrode.

In order to obtain the above mentioned and other objects, the presentinvention provide a reflective transmission type TFT LCD wherein each ofthe reflective pixel electrode and the transmissive pixel electrode isconnected directly to a source electrode of a thin film transistor, orthe transmissive pixel electrode are concurrently formed with gateelectrode and made with double layer of transparent conduction layer andmetal layer which can be used as parameter conduction layer between thetransparent conduction layer and the reflective pixel electrode.

According to one aspect of the present invention, the reflectivetransmission type thin film transistor liquid crystal display (TFT LCD)comprises a glass substrate, at least one thin film transistor on thesubstrate for controlling a pixel, passivation layer having at least onecontact hole in a source region of the thin film transistor, atransmissive pixel electrode which is formed on the passivation layerand is connected with a source electrode of the source region through acontact hole, a reflective pixel electrode which is formed on thepassivation layer and is connected with the source electrode of thesource region through a contact hole. And the pixel area is composed ofa transparent area in which only the transmissive pixel electrode ofwhole pixel electrode exist and a reflective area in which thereflective pixel electrode exist.

Here, it is obvious to those who are skilled in the art that thestructure of thin film transistor can be varied according to the methodof fabrication.

Here, for the prevention of defective chemical reaction among thereflective layer, the transmissive layer and the etchant in the processof etching or cleaning, the reflective transmission type thin filmtransistor liquid crystal display may have a separating insulator layerwhich have good transparency between the transmissive pixel electrodeand the reflective pixel electrode.

If the number of contact hole is one, the transmissive pixel electrode(in case of comprising the separating insulator, the separatinginsulator also) have a hole revealing some part of the source region andthe reflective pixel electrode which is formed over the transmissivepixel electrode is connected with the source electrode of the part ofthe source region via the hole.

In case that the number of contact hole is two, one is for thetransmissive pixel electrode and the other is for the transmissive pixelelectrode, in the region of the other contact hole, the transmissivepixel electrode (in case of having a separating insulator, theseparating insulator also) has a hole revealing the source electrode fora connection between the reflective pixel electrode and the sourceelectrode.

Here, the hole formed in the transparent conduction layer and in theseparating insulator can be formed by sequential forming of the twolayers and patterning of the two layers using one photo mask Generally,the width of the contact hole formed in the source region is far widerthan the thickness of layers forming the pixel electrode, the removal ofsome part of the transmissive conductor layer and the separatinginsulator at the contact hole can be executed in the patterning.

In the present invention, the reflective pixel electrode may be madewith metals including aluminum and the transmissive pixel electrode maybe made with indium metal oxide lineage such as ITO, IZO.

Generally, the transparent area takes form and shape of window in thereflective area. And, the separating insulator can be removed for theefficiency of transmission of backlight by etching process wherein thereflective pixel electrode acts as an etching mask.

In the above explanation, for the efficiency of reflection, thetransmissive pixel electrode are preferably formed before the reflectivepixel electrode are formed. But, the sequence of forming thetransmissive pixel electrode and forming the reflective pixel electrodecan be changed with no significant change of effect.

According to another aspect of the present invention, the reflectivetransmission type thin film transistor liquid crystal display (TFT LCD)comprises a glass substrate, at least one thin film transistor on thesubstrate for controlling a pixel, a first type pixel electrode which isformed and patterned concurrently with gate of the thin film transistor,comprising upper non-oxidizing metal layer removed in transparent areaand lower transparent conductor layer. It also comprises a passivationlayer which is formed over the thin film transistor and over a firsttype pixel electrode. The passivation layer has a contact hole at asource region and a hole (or a window) in the transparent area andneighboring region (in a region including the transparent area). Asecond type pixel electrode which is formed over the passivation layer,is patterned to cover whole pixel area except the transparent windowregion, and is connected with a source electrode of the thin filmtransistor through the contact hole and connected with the non-oxidizingmetal layer of the first type pixel electrode at the neighboring region.

Here, the passivation layer is preferably made with photo-sensitivetransparent insulator and at least at some part the surface of thepassivation layer is treated to take embossment which forms micro lensfor focusing or integrating light. More preferably, the thickness of thepassivation layer times the difference of refraction index correspondsto a quarter of wavelength of light in liquid crystal.

And the non-oxidizing metal can be one selected form the groupconsisting of chromium and tungsten-molybdenum.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages of the present invention willbecome apparent from the following description taken in conjunction withthe accompanying drawings, in which:

FIG. 1 to FIG. 7 are cross sectional views to selected stages of amethod for forming an example according to one aspect of the presentinvention;

FIG. 8 and FIG. 9 are cross sectional views to selected stages of amethod for forming other example of the aspect of the present invention;

FIG. 10 and FIG. 11 are cross sectional views to selected stages of amethod for forming another example of the aspect of the presentinvention;

FIG. 12 shows a cross sectional view of a different example of theaspect of the present invention;

FIG. 13 shows a planar view of the example of FIG. 12;

FIG. 14 a shows a cross sectional view of other different example of theaspect of the present invention;

FIG. 14 b shows a cross sectional view schematically presenting thephase change of light in an example of the present invention.

FIG. 15 shows the planar view of an example of the other aspect of thepresent invention.

FIG. 16 shows the cross sectional view of the example of FIG. 15according to the cut line AA′.

FIG. 17 to FIG. 19 are cross sectional views of different examples ofthe other aspects of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described hereinafter more fully withreference to the attached drawings, wherein preferred embodiment of theinvention are shown. This invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be through and complete, and will fully conveythe scope of the invention to those skilled in the art.

(Embodiment 1)

According to FIG. 1 to FIG. 3, gate electrode 11 is formed on asubstrate 10. Gate insulating layer 13, active layer 15 made withamorphous silicon and Ohmmic contact layer 14 made with doped amorphoussilicon are sequentially formed on the substrate 10 including the gateelectrode 11. By patterning process, the Ohmmic contact layer 14 andactive layer 15 are patterned to define active region. Then, metal layeris formed and patterned to shape a source electrode 16 and a drainelectrode. In the patterning process, the Ohmmic contact layer and upperpart of active layer 15 in the active region are also removed to makechannel of a thin film transistor. As shown in FIG. 3, the source/drainelectrode is larger than the source/drain region of the active region.

Referring to FIG. 4, a passivation layer 17 made with insulating layeris formed on the source/drain electrode and patterned to form contacthole revealing some part of the source electrode 16.

Referring to FIG. 5, on the passivation layer 17, a transmissive pixelelectrode 18 is formed to cover a transparent area. The transmissivepixel electrode 18 can be made by depositing (including physicaldepositing) the transparent conduction layer like ITO and patterning thetransparent conduction layer. In the patterning process, the transparentconduction layer is removed at some part of contact hole to make a holerevealing some part of the source electrode.

With regard to FIG. 6 and FIG. 7, separating insulator 19 made withsilicon nitride is formed on the substrate including transmissive pixelelectrode 18. In the separating insulator 19, a hole is formed to revealthe part of the source electrode 18. Accordingly, when the reflectiveconduction layer made with aluminum neodymium is deposited on theseparating insulator 19, the reflective conduction layer is connecteddirectly to the source electrode 18 through the hole formed in theseparating insulator 19 and transmissive pixel electrode 18. Then, bypatterning the reflective conduction layer, the reflective pixelelectrode 20 having window through which the backlight is transmittedcan be formed. For the efficiency of light transmission in thetransparent area, the separating insulator can be removed in the windowarea by using the reflective pixel electrode 20 as an etching mask.

(Embodiment 2)

According to FIG. 8, a structure of a thin film transistor andpassivation layer 17 are formed on a substrate 10. Then, reflectiveconduction layer made with aluminum containing metal is formed first onthe passivation layer 17 which has contact hole. Through the contacthole the reflective conduction layer is connected to the sourceelectrode 16. By patterning the reflective conduction layer, reflectivepixel electrode 20 having light transmission window is formed andconcurrently a hole is formed at some part of the contact hole. Then,transparent conduction layer made with IZO is deposited (for the presentinvention, sputtering may be a type of physical deposition) andpatterned to form a transmissive pixel electrode.

Compared with ITO layer, the IZO layer has less harmful reaction withaluminum containing metals at the interface. So, separating insulatorcan be omitted. However, if the sequence of forming reflective pixelelectrode and forming transmissive pixel electrode is reversed, the IZOlayer is to be damaged when the aluminum containing layer is patternedto form a light transmission window. Because the etching selectivity forthe two layer is not so different.

(Embodiment 3)

FIG. 10 and FIG. 11 show another embodiment that is slightly changedform the embodiment 1. In the embodiment 1, according to FIG. 5 and FIG.6, the removal of transparent conduction layer and separating insulatorlayer in a contact hole region is made by individual patterning.However, in this embodiment, the hole formed in the transparentconduction layer and in the separating insulator layer is formed bysequential forming of the two layers and by patterning the two layersusing one photo mask. Then, reflective pixel electrode 20 is formed.After the patterning of reflective conduction layer, the separatinginsulator 19 can be etched in the transparent window area for theimprovement of efficiency of light transmission.

(Embodiment 4)

FIG. 12 shows another embodiment of the present invention. A sourceelectrode 16 is extended beyond the active region made with amorphoussilicon layer. In the region of the source electrode 16, two contactholes are formed in a passivation layer 17 which covers the sourceelectrode 16. Then, transmissive pixel electrode 18 made with ITO isformed on the passivation layer 17. Next, a separating insulator 19 madewith silicon nitride or organic insulation material is formed on thetransmissive pixel electrode 18 to cover the transmissive pixelelectrode 18. In the process of forming, the transparent conductionlayer and the separating insulator layer is removed at one contact holeregion. And then, reflective conduction layer is formed on theseparating insulator 19 and patterned to form a reflective pixelelectrode 20 which has light transmission window. Thus, the transmissivepixel electrode 18 is connected to the source electrode 16 through theother contact hole. And the reflective pixel electrode 20 is connectedto the source electrode 16 through the one contact hole.

FIG. 13 is a planar view to the embodiment shown in FIG. 12 and also canbe a reference for the above described embodiments. In a sourceelectrode region, there are two contacts through which pixel electrodesare individually connected to the source electrode. In the middle of apixel region, two light transmission window 27 exist and formtransparent area. Hereinafter more detailed description to the FIG. 13regarding above mentioned embodiments will be made.

On a substrate like glass substrate, a gate line 110 including gateelectrode is formed with metal layer like chromium. Concurrently, acapacitor line 111 is also formed with the same metal layer. Then, gateinsulation layer such as silicon nitride layer is formed on the gateline 110 and the capacitor line 111. And active layer pattern 150 madewith amorphous silicon and Ohmmic contact layer pattern made with N+doped amorphous silicon is formed at least on the gate electrode. Bydepositing and patterning metal layer like chromium, titanium andmolybdenum, a source electrode 162 and a drain electrode 161 which areconnected with the Ohmmic contact layer pattern, data line 160 crossingwith the gate line 110 and the capacitor line 111 and metal pattern 163formed on the capacitor line 111 is made. The metal pattern 163associated with the capacitor line 111 makes an effective means foracquiring capacitance.

Then, passivation layer is formed over the source electrode 162 and thedrain electrode 161. Regarding to embodiment 4 shown in FIG. 12, twocontact holes 171,172 in the source electrode region and one contacthole 173 on the metal pattern 163 are formed by patterning thepassivation layer. Contact holes 173,174 are also formed at the end ofeach data line 160 and gate line 110, i.e. at each data pad and gatepad.

In case of forming the passivation layer with organic insulator, at thesurface of passivation layer, embossment can be made to be micro lenswhich integrates reflected light or transmitting light. And, if thepassivation layer is photosensitive, patterning the passivation layercan be executed by only photolithography process and one etching stepcan be omitted.

Over the passivation layer, transparent conduction layer such as ITO,IZO is deposited and patterned to form a transmissive pixel electrodewhich is connected to the source electrode 162 through one contact hole171. The transmissive pixel electrode 180 is preferably made smallenough to cover only the transmissive area. The transmissive pixelelectrode 180 is also connected with the metal pattern 163 through thecontact hole 173 formed on the capacitor line 111 to be a kind ofcapacitor electrode. Also, the transparent conduction layer can beremained on the pad area where the remained transparent conduction layeract as subsidiary pad. On the transmissive pixel electrode 180, aseparating insulator made with silicon nitride or organic insulator isformed. To reveal the source electrode 162 through the other contacthole 172, the separating insulator and the transmissive pixel electrode180 have hole in them. Then, the reflective pixel electrode 200 formedon the separation insulator is connected with the source electrode 162through the other contact hole 172. The reflective pixel electrode 200can be made with aluminum containing metal or silver containing metaland patterned to form reflective area which covers the whole pixelregion except for the transparent area. The reflective area can beformed over the gate line 110 or the data line 160 to enlarge the wholepixel area.

Generally, the micro lens for integrating light can be made at thesurface of passivation layer by forming embossments at the surface. Ifthe separating insulator is formed with organic material, preferablywith photo sensitive material like polyimide, the micro lens can also bemade at the surface of the separating insulator in place of thepassivation layer. And, in place of the transmissive pixel electrode180, the reflective pixel electrode 200 can be connected to metalpattern 163 to become a capacitor electrode. It is obvious to thoseskilled in the are that, to the embodiment 1˜3, the above descriptioncan be easily applied by mere change of contact between the sourceelectrode and the pixel electrodes.

(Embodiment 5)

FIG. 14 a shows a different type of embodiment of the present invention.A source electrode 16 is formed wide on the substrate in the structureof the bottom gate type thin film transistor. A passivation layer 17 isformed on the substrate including the source electrode 16. A pixelelectrode is formed on the passivation layer 17. The pixel electrodecomprises a transmissive pixel electrode 18, a separating insulator 19and a reflective pixel electrode 20. Both the transmissive and thereflective pixel electrode 18,20 are individually connected to thesource electrode 16 through a contact hole formed in the passivationlayer 17. The separating insulator 19 is formed to prevent the problemscaused by the direct connection of the transmissive pixel electrode 18and the reflective pixel electrode 20. In the middle of a pixel area,there is a transparent area made by removing the reflective conductionlayer. In the transparent area, there is a window formed by patterningthe passivation layer 17. The window in the passivation layer is formedto improve the brightness of LCD. Generally, for the maximum brightness,the Δnd of liquid crystal layer in reflective type LCD correspond to aquarter of wavelength of light and the Δnd of liquid crystal layer intransmissive type LCD correspond to half of the wavelength of light. So,if the crystal layer has same thickness over the whole pixel area in areflective-transmission type LCD like embodiment 4, the transmissivepixel area or the reflective pixel area cannot be in the state ofmaximum brightness in bright mood. Thus, by differentiating thethickness of liquid crystal layer in transmissive region from that inreflective area, the state of polarized light can be matched in phasewith the polarizer film placed at the front side of LCD in bright mood.And at least the brightness of LCD can be improved by partial removal ofthe mismatch in phase. And, considering the above described, thethickness of passivation layer preferably is equal to the thickness ofthe liquid crystal layer in reflective pixel area. In FIG. 14 b, theabove explanation is digested.

(Embodiment 6)

FIG. 15 shows a planar view of pixel area and pad area in an embodimentof the other aspect of the present invention. The sequence of formingreflective pixel electrode and forming transmissive pixel electrode canbe exchanged. Along the peripheral part of transparent area, areflective pixel electrode and a transmissive pixel electrode areconnected each other by a parameter metal layer.

FIG. 16 shows a cross sectional view of the embodiment shown in FIG. 15along the line AA′. To form the structure, first, transparent layer 51and chromium layer 61 are made on the glass substrate 10 and patternedto form gate electrode, gate line, gate pad and transparent layercontaining pixel electrode. The transparent conduction layer 51 can bephysically deposited by sputtering ITO or IZO material, and the chromiumlayer 61 can also be formed by sputtering. The transparent layercontaining pixel electrode is electrically separated with the gateelectrode. The gate insulation layer 13 made with silicon oxide orsilicon nitride is formed by CVD (chemical vapor deposition) method andpatterned to cover the gate electrode and gate line. But the gateinsulation layer is removed on the transparent layer containing pixelelectrode. Amorphous silicon active layer 15 and impurity dopedamorphous silicon ohmmic contact layer 14 are deposited and patterned toform active region. The active region can be divided into source, drainand channel region. Then, the drain electrode, the source electrode 16and data line and data pad are formed by forming metal layer andpatterning the metal layer. Ohmmic contact layer is etched by using themetal layer pattern like the source/drain electrode as an etching maskto make the channel operated properly. A passivation layer 17 made withorganic insulator is formed over the source/drain electrode andpatterned to form a contact hole revealing a part of the sourceelectrode 16 and a window. The window reveals the most part of thetransparent layer containing pixel electrode including a transparentarea and the neighboring part of the transparent area.

The thickness of passivation layer 17 may preferably be equal to thethickness of the liquid crystal layer in reflective pixel area with noregard to the direction of robbing, the tilt angle and other variablesof LCD.

And the surface of the passivation layer 17 may has embossment to formmicro lenses to integrate light. Then, the reflective conduction layerincluding aluminum is formed over the passivation layer 17 and patternedto define the transparent area and to form reflective pixel electrode 20which is connected to the source electrode 16 through the contact hole.

After the patterning the reflective conduction layer, the chromium layer61, the upper layer of the transparent layer containing pixel electrodeis removed by using the reflective pixel electrode 20 as an etchingmask. Thus, the transparent conduction layer 51 in the transparent layercontaining pixel electrode are indirectly connected at the neighboringpart of the transparent area with the reflective pixel electrode 20 bythe parameter chromium layer 61 and also electrically connected with thesource electrode 16 by the reflective pixel electrode 20.

In the above embodiment, transparent layer containing pixel electrodemay be formed with the source electrode in place of the gate electrodeor may be formed with the same kind of double layers at a different stepafter the forming of the source electrode. So, if the transparent layercontaining pixel electrode is formed with the source electrode in placeof the gate electrode, gate electrode may be made with aluminum, thesource/drain electrode layer may be made with transparent layer andchromium, and the reflective pixel electrode may be made with chromiumor aluminum.

(Embodiment 7)

FIG. 17 shows a cross sectional view of a different embodiment of thepresent invention. Here, a part of thickness of a passivation layer 17is remained in the transparent area. Whole pixel electrode comprises atransmissive pixel electrode 20 which is connected to a source electrode16 with no connection through a contact hole. The whole pixel electrodealso comprises a reflective pixel electrode 20 which is separated at themost part by passivation layer 20 and connected through a contact holewith the source electrode 16. Of course, the reflective conduction layeris removed in the transparent area so that the light generated from abacklight can be transmitted to the front side of LCD and thepassivation layer should be transparent.

(Embodiment 8)

FIG. 18 shows a cross sectional view of an embodiment which cancompensate the shortness of the embodiment shown in FIG. 17. In theembodiment shown in FIG. 17, it is difficult to remove the partialthickness of the passivation layer 17 in the transparent region in theprocess of patterning the passivation layer 17 to form a contact hole atsome part of the source electrode region. But, in this embodiment, thepassivation layer 17 is removed thoroughly in the transparent area andthe transmissive pixel electrode 18 has covering 39. Here, Thetransmissive pixel electrode 18 including the covering 39 is formed bydepositing a covering layer made with silicon oxide or silicon nitrideon the transparent conduction layer and patterning the covering layerand the transparent conduction layer with an etching mask. By thecovering 39, the transparent conduction layer like ITO can be separatedwith the reflective conduction layer like aluminum in the process offabrication.

(Embodiment 9)

According to FIG. 19, a transparent layer made with ITO and a metallayer are formed over a source electrode 16 and patterned to form atransparent layer containing pixel electrode. Then a passivation layer17 is formed over the transparent layer containing pixel electrode. Thepassivation layer 17 is patterned to form a contact hole at a part ofthe source electrode 16 and to form a window revealing some part of thetransparent layer containing pixel electrode. And, a reflectiveconduction layer made of aluminum is formed on the passivation layer 17and patterned to define a reflective area. In the patterning of thereflective conduction layer, the reflective conduction layer is removedin the transparent area to reveal the transparent layer containing pixelelectrode. Then, the upper layer of the transparent layer containingpixel electrode, the metal layer 28 is removed by using the reflectivepixel electrode 20 as an etching mask. Compared with the embodimentshown in FIG. 18, the embodiment shown in FIG. 19 have a differentcovering for transmissive pixel electrode 18. The covering, the metallayer 28 is made of metal which can act as a buffer layer between thetransparent conduction layer and the reflective conduction layer. And,finally, the covering is to be removed in the transparent area.

Compared with the embodiment 6 where the transparent layer containingpixel electrode is formed with the same layer for gate electrode, thetransparent layer containing pixel electrode (made with transparentconduction layer and the covering layer) of the present embodiment isformed concurrently with the same layers for the source electrode inplace of the gate electrode or may be formed with the same kind ofdouble layers at a different step after the forming of the sourceelectrode. Then, the covering layer preferably is made with materials ofgood conductivity, metal, like chromium, titanium for the signaltransmission of data line which is concurrently formed with the sourceelectrode or the transparent layer containing pixel electrode.

The above mentioned embodiments are all related with amorphous silicontype and bottom gate type TFT LCD, but the concept of the presentinvention can also be applied to polycrystalline silicon type or topgate type TFT LCDs.

1. A liquid crystal display (LCD) having a transmissive region and areflective region, the LCD comprising: a substrate; a thin filmtransistor (TFT) formed on the substrate and comprising a gateelectrode, a source electrode and a drain electrode; a first pixelelectrode formed on the same plane with the gate electrode, the firstpixel electrode comprising: a transparent conductive layer; and anon-oxidizing metal layer formed on the transparent conductive layer andhaving a first opening corresponding to the transmissive region; apassivation layer formed on the TFT and the first pixel electrode andhaving a contact hole exposing the source electrode and a second openingcorresponding to the transmissive region; and a second pixel electrodeformed corresponding to the reflective region, on the passivation layerand connected to the non-oxidizing metal layer and e source electrodevia the second opening and the contact hole, respectively, the secondpixel electrode having a third opening corresponding to the transmissiveregion.
 2. The LCD of claim 1, wherein the non-oxidizing metal layer isformed of Cr or MoW.
 3. The LCD of claim 1, wherein the transparentconductive layer is formed of indium tin oxide (ITO) or indium zincoxide (IZO).
 4. The LCD of claim 1, wherein the passivation layer isformed of a photosensitive transparent insulating material.
 5. The LCDof claim 4, wherein the passivation layer has embossment on a surfacethereof.